Fluid and mechanically actuated disc brake system

ABSTRACT

The invention concerns improvements in a disc brake assembly that comprises: A. FIRST MEANS OPERABLE IN RESPONSE TO CONTROLLED APPLICATION OF FLUID PRESSURE TRANSMITTED FROM A SOURCE TO ADVANCE A BRAKE PART INTO BRAKING ENGAGEMENT WITH A ROTATING DISC, THE BRAKE PART BEING SUBJECT TO WEAR, AND B. SECOND MEANS OPERABLE IN RESPONSE TO PREDETERMINED DECREASE IN SOURCE FLUID PRESSURE TO EFFECT DISPLACEMENT OF SAID BRAKE PART INTO BRAKING ENGAGEMENT WITH SAID DISC AND IRRESPECTIVE OF THE WORN CONDITION OF SAID PART.

United States Patent Martins [54] FLUID AND MECHANICALLY ACTUATED DISCBRAKE SYSTEM [72] inventor: Samuel J. Martins, Reseda, Calif.

[73] Assignee: Ail-heat Products, Inc., Van Nuys,

Calif.

22 1 Filed: Oct. 15, 1970 1211 Appl. No.: 80,979

[52] US. Cl. ..l88/71. 8, 188/72.6, 188/72.9, 188/106 F, 188/170,188/196P 51 Int.'Cl ..F16d65/52 [58] Field of Search ..188/71.7, 71.8,72.1, 72.4, l88/72.6, 72.9, 72.7, 106 F, 170, 196 P [5 6] ReferencesCited UNITED STATES PATENTS 3,337,008 8/1967 Trachte ..188/l06 F3,371,753 3/1968 Meier ..l88/196 P X 3,599,761 8/1971 Schultz et a1...l88/l70 3,500,969 3/1970 Asher ..l88/106 F 3,155,200 11/1964 Halibrand..188/l96 P Primary Examiner-George E. A. Halvosa Attorney-White,Haefliger & Bachand [5 7] ABSTRACT The invention concerns improvementsin a disc brake assembly that comprises:

a. first means operable in response to controlled application of fluidpressure transmitted from a source to advance a brake part into brakingengagement with a rotating disc, the brake part being subject to wear,and

b. second means operable in response to predetermined decrease in sourcefluid pressure to effect displacement of said brake part into brakingengagement with said disc and irrespective of the worn condition of saidpart.

10 Claims, 8 Drawing Figures P'A'TENTEDIIH a 1' m2 SHEET 1 (IF 4 FLUIDAND MECHANICALLY ACTUATED DISC BRAKE SYSTEM BACKGROUND OF THE INVENTIONThis invention relates generally to disc brakes, and more particularlyconcerns disc. brake lining wear compensation.

It is desirable in certain disc brake installations to provide for bothfluid pressure responsive brake application and auxiliary mechanicalapplication of the brake. Such dual mode braking is of advantage, forexample, in vehicles where provision for emergency mechanical braking ismade in addition to the normal fluid pressure responsive brakeapplication.

Where a fluid pressure responsive plunger is employed to urge the brakelining toward the disc, wear of such lining is not an impediment tofluid pressure operation of the brake, since more fluid is simplydisplaced into the cylinder to stroke the plunger; however, such wearpresents a serious problem as respects auxiliary mechanically effectedstroking of the plunger inasmuch as mechanical linkages have limitedranges of movement, and mechanical advantage may tend to lessen withincreasing length of the piston stroke to effect braking.

A highly advantageous way of overcoming the latter problem involves theprovision of load transmitting shoulders carried by the plunger and byauxiliary means to mechanically advance the plunger toward the disc ormoving part to braked, such shoulders being located for relativeshifting, in response to predetermined plunger advancement, to blockretraction of the plunger in such manner as to compensate for brakelining wear, as disclosed in that certain Gilliland et al applicationSer. No. 853,678 for U.S. Letters Patent entitled, Disc Brake WearCompensation, filed August 28, 1969, now US. Pat. No. 3,610,375. Afurther problem introduced by the use of such shoulders has to do withre-setting them when the worn brake lining is to be replaced, therebeing need for the provision of structure 'and mode of operationenabling quick and simple re-setting of theshoulders.

SUMMARY OF THE INVENTION It is a major object of the invention toprovide, in a disc brake assembly, apparatus characterized as overcomingthe above problem, and also as adding unusually advantageous structureand braking functions.

Basically, the invention concerns the provision, in such a disc brakeassembly, of first means operable in response to controlled applicationof fluid pressure transmitted from a source to advance a wearable brakepart into braking engagement with a rotating disc, together with secondmeans operable in response to predetermined decrease in source fluidpressure to effect displacement of the brake part into brakingengagement with the disc, and irrespective of the worn condition of thatpart. Such first means may typically comprise a plunger and cylinderassembly, and the second means may comprise elements having wedginginterengagement characterized as shiftable in response to an increase inthe extent of such brake part advancement due to wear, to compensate forthe latter. Also, the second means may advantageously include a lever,yieldable means operable to pivot the lever in response to the decreasein source fluid pressure, and structure operable in response to leverpivoting to urge one of the elements in a direction to advance the brakepart toward the disc, as described.

Further, the referenced structure may with unusual advantage include aram body receiving the elements a second of which has wedging interfitwith the body and also with the first element which moves with theplunger; also, the second element may be wedge shaped and located to beeasily reset relative to said one element as required during replacementof a worn brake part or pad carried by the plunger.

Additional objects and advantages of the invention include the carriageof the first and second means as described by a caliper adapted tostraddle the disc during rotation of the latter, the caliper mounted toshift bodily in opposite directions relative to the disc in order tobring brake parts or pads: in opposite sides of the disc into engagementwith those sides in response to fluid pressure application; and theprovision of pad retraction mechanism as will be described.

These and other objects and advantages of the invention, as well as thedetails of an illustrative embodiment, will be more fully understoodfrom the following description and drawings, in which:

DRAWING DESCRIPTION FIG. 1 is an end elevation showing a disc brakecaliper structure;

FIG. 2 is a section taken on line 2--2 of FIG. 1;

FIG. 3 is an enlarged section showing details of the brake actuatorappearing in FIG. 2;

FIG. 4 is a section taken on line 4-4 of FIG. 3;

FIG. Sis a view like FIG. 4, but showing a modified position of themechanism; FIG. 6 :is a view showing resetting of the brake structure;

FIG. 7 is a diagrammatic showing of a retractable caliper assembly;

FIG. 8 illustrates a modified form of the invention.

DETAILED DESCRIPTION Referring first to FIG. 7 (showing an environmentin which the invention is particularly useful) the illustrated discbrake assembly 10 includes a caliper 11 adapted to straddle the rotarydisc 12 during disc rotation relative to the caliper and about axis 13;a braking element (as for example pad 14) carried by the caliper to faceone side of the disc; means (as for example fixed shaft 15) mounting thecaliper to shift in one direction (see arrow 16) in order to bring thebraking element into braking engagement with one side face 12a of thedisc in response to actuating force exertion on the caliper; andretractor means generally indicated at 17 carried to resist suchshifting of the caliper and to displace the caliper in the oppositedirection to carry the braking element out of engagement with the discin response to reduction of actuating force exertion. In this regard,the retractor means 17 includes a compression spring 18 operativelyconnected between shaft 15 and the caliper to be compressed in responseto caliper shifting in the direction of arrow 16. Note that spring 18 isheld endwise between a part (as for example washer 19) on the shaft, anda shoulder 20 integral with the caliper, as for example via bracket 21.

Also shown in FIG. 7 is an actuator, as for example piston 22, carriedby the caliper and another braking element, as for example pad 23,carried to be operable by the actuator to engage the opposite side 12bof the disc, whereby the actuator then exerts the previously mentionedactuating force on the caliper. For example, when fluid pressure fromsource 24 is transmitted via line 25 and valve 26 to the cylinder 27,the piston 22 is urged to the right to engage pad 23 with the disc 12.Reaction force transmitted by the fluid pressure on the caliper urgesthe latter to the left until pad 14 engages the disc 12, so that bothpads then frictionally grip op posite sides of the disc with brakingeffect. Such shifting of the caliper results in compression of spring18. Upon release of pressure application, the caliper 11 and pad 14automatically retract a predetermined distance d to the right inresponse to expansion of spring 18, whereby the pad 14 is held out ofengagement with the disc until such time as the brake is again actuated.Also, the pad 23 is automatically retracted a predetermined distance d,plus a to left, as by means of retractor mechanism 28, to compensate forthe rightward movement d, of the caliper and to carry the pad 23 out ofengagement with the disc until such time as the brake is again actuated.Retractor mechanism 28 may be similar to that shown at 17, and includesa shaft 29 integral with piston 22, a washer 30 on the shaft, and acompression spring 31 retained between the washer and the face 32 of thecaliper. Accordingly, when fluid pressure exerted on piston 22 isrelieved, the elements operation. Vehicle wheel structure (not shown) ismounted on a shaft which turns about axis 43, and attachment structureconnects a braking disc 45 to the shaft.

The assembly 39 includes a caliper 46 straddling the disc 45, brakingelement or pad 47 carried by the caliper to face one side 45a of thedisc; means mounting the caliper to shift in one direction (see arrow48) in order to bring braking element 47 into braking engagement withdisc side face 45a in response to actuating force exertion on thecaliper; and retractor means carried to resist such shifting of thecaliper and to displace the latter in the opposite direction to carrythe pad 47 out of disc engagement in response to reduction of actuatingforce exertion. In this regard, the mounting means includes a pair ofparallel shafts 50 (corresponding to shaft in FIG. 7) extendingoutwardly of the disc periphery and at locations at opposite sides ofaxis 43 and non-rotary axle 49. Thus, the shafts may be spaced about theaxis 43 at any included angle. The shafts are integral with oppositelyextending torque arms 51 projecting from a hub 52 bolted at 53 to theaxle flange 54. The torque arms are connected to the shafts 50.

By locating the fixed shafts 50 at opposite sides of the axis 43, theL-shaped caliper body 46 is enabled to be supported by the shafts 50 andtorque arms 51 in a balanced condition. This further facilitates the useof two actuators generally indicated as housed at 55 and 56 in thecaliper body 46. Such actuators may include pistons mounting brake padsand corresponding to piston 22 and brake pad 23 in FIG. 7.

Turning now to FIGS. 2-6, the invention broadly concerns the provisionof first means, operable in response to applications of primary brakingforce, to advance a brake part (as for example pad 58 which is subjectto wear) into braking engagement with a relatively rotating disc; asource of fluid pressure, as for example is indicated at 59; and, secondmeans operable in response to predetermined decrease in such fluidpressure application to effect displacement of the brake part (or pad)into braking engagement with the disc, irrespective of variousconditions of wear of that part 58. Such first means may typicallycomprise a plunger and cylinder assembly, the plunger responsive tofluid pressure application (as from source 59) to advance relative tothe cylinder to transmit actuating force to ad vance the brake pad; inaddition, the referred to second means may with unusual advantageinclude elements having wedging interengagement characterized asshiftable in response to an increase in the extent of such plungeradvancement due to brake pad wear, to compensate for such wear.

In the example shown, the piston or plunger 116 is movable in thecylinder 106 to advance the plate 113 which carries the brake pad 58subject to wear. A fluid pressure supply line for the cylinder isindicated at 124, with a master control valve at 124a. Such pressure issupplied to the space behind the piston.

The referred to second means may advantageously include one element (asfor example tapered tenninal 116a on plunger extension or stem 116k)adapted to be urged to the left in FIG. 3 to displace the pad 58 intoengagement with the rotating disc, as described. Such second means mayalso include another element or elements, such as wedge-shaped bodies129, and a ram body 131 which is tubular to receive the elements 116aand 129. A lever is pivoted at 128 to transmit force to the convex endportion 131a of the ram body to urge the elements 129 and 116b to theleft, as described. In this regard, FIGS. 3-5 show the bodies 129 havingtapered interfit with the recess walls 126 in the ram body, and with thetapered opposite sides 125 of the element 116a. The axial taper at walls126 is greater than at sides 125 to facilitate resetting of the bodies129, as will be described.

Application of fluid pressure via duct 124 to the plunger faces 134tends to drive the plunger forwardly (leftwardly in FIGS. 2 and 3)against resistance imposed by a yieldable means such as the Bellevillespring washers 135 and 136, whereby when the fluid pressure is relievedthe plunger will be retracted rightwardly as the tapered spring washersexpand. In this regard, annulus 137 is retained as shown between thewasher 136 and a ring 138 coupled to the plunger, to transmit loadingbetween the plunger and washers. Washer 135 bears against a flange 139on a sleeve 140 to define a stop for the washers which isself-adjustable in accordance with brake lining wear as will appear.Another ring 141 coupled to the sleeve 140 stops rearward retraction ofthe plunger relative to the sleeve 140 by engaging the annulus 137 whichmoves with the response to predetermined force application. In thisregard, as the lining wears and the plunger is sufficiently urged to theleft in FIG. 3 by fluid pressure application, the resistance imposed bythe drag ring 144a will be overcome by the force generated upon collapseof Belleville washers-135 and 136. Accordingly, the retraction structureof the brake is self-compensating with lining wear.

As the lining wears, and the plunger 116 and extension 116k aredisplaced to the left, the tapered terminal 116a is withdrawn to theleft from between the wedge elements or bodies 129, as is seen in FIG.5. At the same time, the compression spring 144 carried by the cylinderinsert 106a urges the bodies 129 to the right relative to the ram body131, and along tapers 126. This assures that the ram body remainsmechanically connected to the plunger 116 to enable effective auxiliarybraking should the fluid pressure in line 124 fail. In suchcircumstances, the lever 130 is pivoted counterclockwise in FIG. 2, inresponse to force exertion by a'spring 145 to urge the ram body 131 tothe left along with the plunger 116 now mechanically connected to thelever via the wedge bodies 129. Accordingly safety is enhanced in anemergency. Note that a stop shoulder 180 on the ram element is engagablewith the shoulder 181 on insert 106a to limit leftward travel of theram.

Normally, the fluid pressure supplied from source 59 is exerted againstthe face 146 of a piston 147 working in caliper body bore 148 to holdthe spring 145 in compressed and retracted condition via a stern 149 anda cap 150 connected with the piston 147. The rightward terminal 149a ofthe stem engages the lever 130, as shown. Fulchrum point 128 of thelever is adjustable by means such as jack screw 151. A line 152 may beconnected with the lever to relieve its force exertion at 153 againstthe ram 131, after such an emergency.

At such times as the lining or pad 58 is replaced, the wedge parts 129may be reset by means now to be described. FIGS. 5 and 6 show tongs 183introduced through side openings 184 in the ram body 131 to pivot andengage the wedge bodies 129, urging them to the left so as to open thegap between them allowing rightward displacement of the stern portion116a from FIG. 5 to FIG. 4 positions, for example. Accordingly, themechanism may be quickly reset when a new brake lining or pad isinserted.

The unusual combination of advantages of the invention includesprovision for fluid actuation of the brake coupled with mechanicalautomatic actuation in event of an emergency, automatic wearcompensation and take-up as respects both fluid and mechanical elements,provision for re-setting of the mechanical takeup when the lining isreplaced, manual release of the automatically actuated brake, andincorporation of the above in a floating caliper brake unit as used in adiscbrake environment.

In FIG. 8, brake pads 200 and 201 are shown at opposite sides of rotarydisc 202. Caliper 203 straddles the disc to shift in accordance with thedescription in FIG. 7. Plunger 204 is movable in bore 205 to advance thepad 201 toward the disc, and in response to application to side 204a ofthe plunger of fluid pressure supplied via line 206 to space 207.

Plunger extension or stem 208 is secured to the plunger, and has atapered terminal 208a'structurally and functionally related to the wedgeshaped bodies 209 and tubular ram body 210 in the same manner ascorresponding elements 116a, 1129 and 131 described in connection withFIGS. 2-6.

Lever 211 has pivotal connection at 212 with the fitting 213 adjustablysecured at 214 to the caliper body, to permit adjustment of the fulchrumpoint of lever pivoting. The lever urges ram 210 to the left in responseto rightward movement of a cable 215 connected to a brake handle orlever, so that mechanical actuation is well adapted to use duringparking of a vehicle, or during an emergency.

Spring 220 urges bodies 209 toward the right, and sleeve 221 carried bycaliper body centers the stem 208.

I claim:

1. In combination:

a. a disc brake caliper body,

b. a brake pad and a piston and cylinder assembly carried by said bodyand operable in response to fluid pressure application to the piston tourge the pad against the disc, and

c. a ram body having an internal tapered surface and structure couplingsaid ram body to the piston to urge the latter toward the disc inresponse to auxiliary force transmission,

d. said structure including a piston extension, having a taperedterminal and a wedge element having wedge coupling with both saidtapered terminal and the ram body internal tapered surface toaccommodate relative shifting of the piston and said extension towardthe disc as the pad wears, while maintaining the ram body coupled tosaid piston extension for auxiliary force transmission, said ram bodyhaving a side opening to exteriorly expose said wedge element containedwithin the ram body for adjustment shifting out of wedge couplingrelation with said piston extension to permit retraction thereofrelatively away from the disc, the ram body projecting openly and freeof confinement by the caliper body.

2. The combination of claim 1 including a piston stem carried to advancewith said piston in response to said application of fluid pressurethereto, there being a supportsleeve carried by the cylinder and aspring connected between the cylinder and sleeve to resist stemadvancement in the sleeve and to retract the stern relative to thesleeve in response to decreased fluid pressure applicator to the piston,there also being a drag part carried by the cylinder to frictionallyresist advancement and retraction of the sleeve, such resistance beingovercome by piston induced sleeve displacement to compensate for brakepart wear.

3. The combination of claim 1 including a spring urging the wedgeelement toward wedge coupling relation with the piston extension and rambody.

4. The combination of claim 1 wherein said brake pad is carried at oneside of the disc, and including another brake pad carried by the caliperbody at the opposite side of the disc.

5. The combination of claim 4 including means mounting the caliper bodyto shift in opposite directions relative to the disc in order to bringsaid brake pads into engagement with opposite sides of the disc inresponse to said fluid pressure application.

6. The combination of claim 5 including retractor means to retract saidpiston and to shift said caliper body in response to reduction of saidprimary braking force, and tending to disengage said braking pads fromengagement with opposite sides of the disc.

7. The combination of claim 1 including auxiliary force transmittingmeans located to transmit force urging the ram body in a direction tourge the piston toward the disc.

8. The combination of claim 7 wherein said means includes a leverpivotally connected to said caliper body.

9. The combination of claim 8 wherein the lever has a fulchrum, andincluding means to adjustably position said fulchrum.

10. The combination of claim 8 including a spring operable to pivot thelever to exert braking force in response to a decrease in said fluidpressure, and another piston operatively connected to said lever andnormally responsive to application of said fluid pressure to overcomethe spring to prevent said pivoting of said lever.

1. In combination: a. a disc brake caliper body, b. a brake pad and apiston and cylinder assembly carried by said body and operable inresponse to fluid pressure application to the piston to urge the padagainst the disc, and c. a ram body having an internal tapered surfaceand structure coupling said ram body to the piston to urge the lattertoward the disc in response to auxiliary force transmission, d. saidstructure including a piston extension, having a tapered terminal and awedge element having wedge coupling with both said tapered terminal andthe ram body internal tapered surface to accommodate relative shiftingof the piston and said extension toward the disc as the pad wears, whilemaintaining the ram body coupled to said piston extension for auxiliaryforce transmission, said ram body having a side opening to exteriorlyexpose said wedge element contained within the ram body for adjustmentshifting out of wedge coupling relatIon with said piston extension topermit retraction thereof relatively away from the disc, the ram bodyprojecting openly and free of confinement by the caliper body.
 2. Thecombination of claim 1 including a piston stem carried to advance withsaid piston in response to said application of fluid pressure thereto,there being a support sleeve carried by the cylinder and a springconnected between the cylinder and sleeve to resist stem advancement inthe sleeve and to retract the stem relative to the sleeve in response todecreased fluid pressure applicator to the piston, there also being adrag part carried by the cylinder to frictionally resist advancement andretraction of the sleeve, such resistance being overcome by pistoninduced sleeve displacement to compensate for brake part wear.
 3. Thecombination of claim 1 including a spring urging the wedge elementtoward wedge coupling relation with the piston extension and ram body.4. The combination of claim 1 wherein said brake pad is carried at oneside of the disc, and including another brake pad carried by the caliperbody at the opposite side of the disc.
 5. The combination of claim 4including means mounting the caliper body to shift in oppositedirections relative to the disc in order to bring said brake pads intoengagement with opposite sides of the disc in response to said fluidpressure application.
 6. The combination of claim 5 including retractormeans to retract said piston and to shift said caliper body in responseto reduction of said primary braking force, and tending to disengagesaid braking pads from engagement with opposite sides of the disc. 7.The combination of claim 1 including auxiliary force transmitting meanslocated to transmit force urging the ram body in a direction to urge thepiston toward the disc.
 8. The combination of claim 7 wherein said meansincludes a lever pivotally connected to said caliper body.
 9. Thecombination of claim 8 wherein the lever has a fulchrum, and includingmeans to adjustably position said fulchrum.
 10. The combination of claim8 including a spring operable to pivot the lever to exert braking forcein response to a decrease in said fluid pressure, and another pistonoperatively connected to said lever and normally responsive toapplication of said fluid pressure to overcome the spring to preventsaid pivoting of said lever.